'I feel for my American colleagues and what they've had to deal with,' one British climate scientist said.

The harassment faced by U.S.-based climate scientists has been well documented in the media—but not the harassment of scientists in Europe, Canada or the rest of the world.

That's because there hasn't been much to report.

While outspoken scientists of human-caused climate change in the United States endure torrents of freedom of information requests, hate mail and even death threats from skeptics, their counterparts abroad have been free to do their work without fear.

Jochem Marotzke, managing director of the Max Planck Institute for Meteorology in Hamburg, said there is "no systematic attempt by a political camp" to target climate scientists in Germany. "I get the odd critical email from a skeptic, but would not classify anything as personally aggressive," said Marotzke. "Very different from the U.S. scene."

"I feel for my American colleagues and what they've had to deal with," saidTim Lenton, an earth system scientist who specializes in climate tipping points at the University of Exeter in the UK. Lenton said he has never had to fend off skeptic attacks against his work or his integrity. "British scientists aren't immune to attacks, but it is a very different level than compared to what is happening in the U.S."

InsideClimate News contacted scientists working on climate change in Europe, Canada and Japan and learned that virtually everyone believes that the harassment is specific to the United States. They said that it could have long-term consequences for public understanding of global warming.

"The harassment has an intimidating effect—especially on young scientists," said Stefan Rahmstorf, head of earth system analysis at the Potsdam Institute for Climate Impact Research in Germany. Rahmstorf said that watching colleagues be harassed often deters them from speaking to media or the public about their research, which skews the debate.

Climategate, for instance, the 2009 hacking of emails from the University of East Anglia's Climatic Research Unit in the UK, "had a significant impact" on public opinion, he said. During that scandal, U.S. skeptics pounced mainly on emails written by Michael Mann, director of the Earth System Science Center at Penn State University, as evidence that he and others were overstating the human influence on global warming. In a yet-to-be-published Yale study, nearly 13 percent of on-the-fence Americans in 2010 said climategate reduced their trust in climate science and in scientists, Leiserowitz said.

The most recent global poll from 2011 found that only 48 percent of Americans believe climate change is occurring from either human activity or a mix of human and natural causes, the lowest among developed countries. Eighty-three percent of people in Asia expressed this opinion, which was shared by 72 percent in Canada, 69 percent in Europe and 65 percent in Latin in America.

Why Harassment Here and Not There?

U.S. skeptics ramped up efforts a few years ago when momentum built in Washington in both political parties for national climate policies, following the seminal 2007 report of the UN Intergovernmental Panel on Climate Change, which concluded that Earth is warming mainly from fossil fuel emissions.

Their campaigns coincided with the rise of the Tea Party movement, whose members are far more dubious about the science of global warming than the public at large, adding to the growing chorus of skepticism.

There are two main types of harassment in the United States—by individual skeptics, or by campaigns led by conservative groups, often bankrolled by fossil fuel industries, that seek to sow confusion on the climate issue and undermine support for carbon regulations.

Their tactics have included filing onerous Freedom of Information requests that can overwhelm a scientist's workload and force them put their research on hold; barraging scientists with hate mail; and filling online comment boards with claims that researchers manipulated their results.

The foreign scientists interviewed for this story expressed concern about the intimidation and about the state of America's climate debate. They have their own opinions about why this country—and not their own—has become fertile ground for skeptics.

Weak Political Leadership

Lenton, the scientist from the University of Exeter, said he believes it comes down to political leadership, which helps to increase public confidence in the science, and to deter skeptics.

"Governments here [in the UK and Europe] have largely accepted ... that we've got to massively cut our carbon emissions and change our whole way of doing things by 2050," Lenton said. When climate scientists talk to politicians or to the public on climate dangers "one ends up preaching to the converted," he said of Europe.

The UK has pledged to cut emissions by at least 34 percent by 2020, and 80 percent by 2050. The government has funded climate science education at home and has even extended those efforts abroad. The Foreign and Commonwealth Office (FCO) gave about $20,000 to the U.S.-based Environmental Defense Fund to help fund a project to counter climate skepticism in the Texas State Legislature, the Guardian reported earlier this year.

The European Union, home to the world's largest carbon market, has promised a 20 percent reduction of emissions by 2020, and says it would increase that to 30 percent by 2020 if other major emitters agree to the same. Germany is undergoing an energy transformation on a massive scale to replace its retiring nuclear fleet with renewable power.

In contrast to Europe, climate policies in the United States are dead for the foreseeable future, and climate skepticism has become a tenet of Republican politics. GOP presidential nominee Mitt Romney has reversed his earlier position that human activities cause global warming. Even Barack Obama has steered clear of climate change, despite research showing that he would benefit from addressing it.

Lack of political leadership alone, however, doesn't explain the harassment in the United States.

Stephen Harper's Conservative government in Canada has pulled the country out of the Kyoto Protocol, the 1997 global treaty to reduce greenhouse emissions, and has appointed several climate skeptics to crucial federal scientific bodies, including the Natural Sciences and Engineering Research Council and the Canada Foundation for Innovation. Yet Canadians still have some of the world's strongest belief that global warming is happening—and harassment of scientists is not on the scale of its southern neighbor.

"We are generally left alone to do our work," said Bruno Tremblay, a climatologist at McGill University in Montreal, Canada. Tremblay said that unlike many conservative Americans, Canadians generally don't harness suspicions about the government overstepping its powers by trying to control carbon emissions and conserve energy, and in fact they encourage it. So the skeptics' message doesn't mesh with them, he said.

"The incidents reflect two unfortunate things," Leshner said in an interview, "we live in a society where ideologies trump our willingness to hear what science says, and in a country where free speech is so widely valued, people are being attacked."

The foreign scientists interviewed for this story generally agreed that religion and ideology play a bigger role in U.S. politics than they do in their own countries. "This inevitably means things are more about belief than about evidence in the U.S.," said Lenton of the University of Exeter.

According to a 2012 poll by Yale and George Mason Universities, Americans' climate change beliefs divide along party and ideological lines. Among those who said they were "alarmed" or "concerned" about global warming, more than two-thirds identified themselves as Democrat, Independent, or moderate or liberal. In contrast, less than 15 percent of Republicans or conservatives described themselves as alarmed or concerned.

Generally, the more conservative the Republican, the more likely they are to flat-out deny the existence of climate change. Former presidential candidate Rick Santorum, for instance, referred to the acceptance of global warming as a "pseudo-religion" in a column earlier this year for Red State.

Australia Steps Up Climate Efforts Amid Harassment

After the United States, the country with the most harassment by skeptics is Australia. Most speculate that's because the country is the largest exporter of coal in the world. Coal industry groups in Australia have sought to cast doubt on climate science and have lobbied against carbon emission limits. But political will for climate action has been strong enough to counter their opposition.

Last month Australia joined the EU and New Zealand in putting a price on carbon dioxide emissions, and will launch a carbon trading scheme in 2015.

German climatologist Hans Joachim Schellnhuber, director of the Potsdam Institute for Climate Impact Research and a scientific advisor to Chancellor Angela Merkel, was reportedly threatened in Melbourne last year during a guest lecture, when a member of the audience stood up and brandished a noose at the scientist.

The incident led Schellnhuber to declare in an interview earlier this year that it was only a matter of time before deniers kill a climate scientist. Last year, several researchers at the Australian National University in Canberra, located in the southeastern part of the country, had to be relocated to a secure facility after they received a deluge of threats from skeptics.

Beyond the safety of the scientists, "the worrying thing is the message that is sent to the public," said Tremblay of McGill—that the science isn't settled when it is. "[The harassment] just serves to polarize the debate even further. People need to start speaking about this issue for what it is, and leave political and other agendas on the side."